CN115472816A - A kind of silicon oxide particle and its preparation method and application - Google Patents

Abstract

The present invention relates to a kind of silicon oxide particle for electrode material, it is characterized in that, described silicon oxide particle comprises: silicon oxide particle, its general formula is SiOx; Carbon layer, a plurality of described silicon oxide particles are formed by the A carbon layer is bonded, and the plurality of silicon oxide particles to which the carbon layer is bonded is covered by the carbon layer. The silica particles of the invention are compact, have narrow particle size distribution, small specific surface area, and have the advantages of high capacity, high coulombic efficiency, low expansion, high cycle retention rate and the like.

Description

A kind of silicon oxide particle and its preparation method and application

This application is a divisional application of an invention patent application with the application number 201911007418.4, the application date is October 22, 2019, and the invention title is "a silicon oxide particle for electrode material and its preparation method and application".

technical field

The invention relates to the field of batteries, in particular to a silicon-oxygen particle used as a lithium ion electrode material and a preparation method and application thereof.

Background technique

Due to the rapid development and wide application of various portable electronic devices, electric vehicles, and energy storage systems in recent years, the demand for lithium-ion batteries with high energy density and long cycle life has become increasingly urgent. At present, the anode material of commercial lithium-ion batteries is mainly graphite, but due to the low theoretical capacity, the further improvement of the energy density of lithium-ion batteries is limited. Since the silicon anode material has the advantage of high capacity that other anode materials cannot match, it has become a research and development hotspot in recent years, and has gradually moved from laboratory research to commercial application. Among them, the elemental silicon negative electrode material has a serious volume effect in the process of intercalation and extraction of lithium, and the volume change rate is about 300%, which will cause the pulverization of the electrode material and the separation of the electrode material and the current collector. In addition, due to the continuous expansion and contraction of the silicon negative electrode material during the charging and discharging process of the battery and continuous rupture, the resulting fresh interface will form a new SEI film when exposed to the electrolyte, thereby continuously consuming the electrolyte and reducing the cycle performance of the electrode material. .

The existing silicon anode materials have low coulombic efficiency, large expansion, low cycle retention rate, large polarization, and complex preparation process, so it is difficult to realize commercial application in batteries, which is a technical problem in the field.

Contents of the invention

One of the purposes of the present invention is to provide a silicon-oxygen composite material with high capacity, high coulombic efficiency, long cycle life and low expansion rate for lithium-ion batteries and a preparation method thereof for the deficiencies of the prior art.

Specifically, the present invention proposes a silicon-oxygen particle used as an electrode material, which has a dense structure and no pores above the submicron level; it is characterized in that the silicon-oxygen particle includes:

Silicon oxide particles, the general formula of which is SiOx; the silicon oxide particles are formed by the disproportionation reaction of amorphous silicon oxide powder raw materials, for example, to form silicon nanocrystals/amorphous nanocrystals present in the SiOx matrix. Cluster;

A carbon layer, a plurality of the silicon oxide particles bonded by the carbon layer, and a plurality of the silicon oxide particles bonded by the carbon layer are covered by the carbon layer. Specifically, each silicon oxide particle is a secondary particle composed of a plurality of silicon oxide particles and a carbon film, and there is no single primary silicon oxide particle or primary silicon oxide particle coated with a carbon film.

Specifically, the carbon layer material is composed of glucose, sucrose, chitosan, starch, citric acid, gelatin, alginic acid, carboxymethyl cellulose, coal tar pitch, petroleum pitch, phenolic resin, tar, naphthalene oil, anthracene oil, The combination of one or more precursor materials in polyacrylic acid, polyacrylate, polystyrene, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, epoxy resin, polyacrylonitrile, polymethylmethacrylate obtained by carbonization.

Specifically, in the silicon oxide particles, 0.5≤x≤1.5, preferably 0.8≤x≤1.2. More preferably, 0.9≤x≤1.1.

Further, the median diameter D50 of the silicon oxide particles is 0.05-20 μm, preferably 0.3-10 μm. More preferably, the D50 of the silicon oxide particles is 3-8 μm, and D90=3.5-15 μm.

Specifically, the mass ratio of silicon oxide particles to the silicon oxide particles is 80-99.9 wt%, preferably 90-99.5 wt%. More preferably, the mass ratio of silicon oxide particles to the silicon oxide particles is 94-98wt%.

Further, the silicon-oxygen particles may also include conductive additives uniformly dispersed in the inner and/or outer surface carbon layers of the silicon-oxygen particles.

Specifically, the conductive additive may be selected from one or more combinations of Super P, Ketjen Black, vapor-grown carbon fiber, acetylene black, conductive graphite, carbon nanotubes, and graphene.

Specifically, the mass ratio of the conductive additive to the silica particles is 0.01-10wt%, preferably 0.03-5wt%.

Further, the silicon-oxygen particles further include one or more additional carbon layers, preferably one layer, coated on the outer surface of the silicon-oxygen particles.

Specifically, the additional carbon layer is obtained by carbonizing a combination of one or more precursor materials of coal pitch, petroleum pitch, polyvinyl alcohol, epoxy resin, polyacrylonitrile, and polymethyl methacrylate.

Optionally, the additional carbon layer is made of any one of methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, butadiene, benzene, toluene, xylene, styrene or phenol or Various combinations are obtained by chemical vapor deposition.

Further, the mass ratio of the additional carbon layer to the silicon-oxygen particles is 0.1-10wt%, preferably 0.3-6wt%.

Further, as for the silicon-oxygen particles described in any one of the preceding items, the D50 of the silicon-oxygen particles is 1-40 μm, preferably 3-20 μm.

Further, the particle size distribution of the silica particles is narrow, and its span value (SPAN)=(D90-D10)/D50 is ≤1.4, preferably ≤1.35.

Preferably, the specific surface area of the silicon oxide particles is 0.1-10 m ² /g, more preferably 0.3-6 m ² /g.

Further, the tap density of the silica particles is ≥0.6 g/cm ³ , preferably ≥0.8 g/cm ³ .

More specifically, as for the silicon-oxygen particles described above, the silicon-oxygen particles are preferably: D50 = 3.5-10 μm, SPAN = 0.9-1.35, and a specific surface area of 0.8-2.7 m ² /g.

More preferably, the silica particles have D10=3.5-5.5 μm, D50=6.0-10 μm, SPAN=0.9-1.2, specific surface area of 0.9-1.6 m ² /g, and tap density of 0.95-1.2 g/cm ³ , the carbon content is 2-6.5wt%. Most preferably, D10=4.0-5.0 μm, D50=6.5-9 μm, SPAN=0.9-1.1, specific surface area 0.9-1.4m ² /g, tap density 1.0-1.2g/cm ³ , carbon content 2.5- 5.5 wt%.

The present invention also proposes the application of the silicon-oxygen particles described above in electrode materials.

The present invention also proposes a negative electrode material, including the silicon-oxygen particles as described in the preceding one. Wherein, the negative electrode material is prepared by mixing silicon oxide particles and carbon-based powder materials, and the carbon-based powder materials can be selected from natural graphite, artificial graphite, surface-modified natural graphite, hard carbon, soft carbon or mesophase carbon microparticles. Any combination of one or more of the balls.

The present invention also proposes a pole piece or a battery comprising the negative electrode material as described above. In particular, lithium-ion batteries may be used.

The present invention also proposes a method for preparing silicon-oxygen particles as described above, which includes: mixing and granulating silicon oxide particles with carbon layer precursor materials and then carbonizing them in a non-oxidizing atmosphere, and the carbonized products are dispersed , sieving, demagnetization treatment.

Further, the method for preparing silicon oxide particles as described above may also include the addition of conductive additives, specifically, mixing and granulating silicon oxide particles, conductive additives, and carbon layer precursor materials in a non-oxidizing atmosphere Carry out carbonization in the middle, and the carbonized product is dispersed, sieved, and demagnetized.

Further, the aforementioned method further includes the step of coating one or more additional carbon layers, preferably one layer.

Specifically, the granulation equipment can be selected to have both heating and stirring functions, including but not limited to VC mixers, mechanical fusion machines, coating tanks or reaction tanks. Specifically, during the granulation process, the linear velocity at the maximum diameter of the stirring part in the VC mixer, mechanical fusion machine, coating kettle or reaction kettle is 1-30m/s; the temperature can be selected from 100-1050°C, and the time is 0.5-10 hours, and protected by an inert atmosphere. During this process, the carbon precursor material softens and is evenly coated on the surface of the silicon oxide particles during the continuous high-speed stirring process. At the same time, multiple silicon oxide primary particles coated with the carbon precursor are bonded and agglomerated with each other A silicon oxide/carbon precursor composite secondary particle of a certain size is formed. The above-mentioned secondary particles will become denser under long-term and high-frequency shearing, extrusion, and collision in VC mixer, mechanical fusion machine, coating kettle or reaction kettle, and at the same time, the carbon precursor body will be partially removed under heating conditions. Molecular volatiles, partially cross-linked, carbonized, thereby setting the secondary particles.

Specifically, the granulation equipment may also be a spray drying equipment. At this time, when the spray drying equipment processes the slurry containing silicon oxide particles and carbon precursors, the nozzle of the equipment atomizes the slurry into small droplets, and the solvent in the droplets is heated by the hot air at a certain temperature in the equipment. evaporate rapidly under the environment, and obtain dry silicon oxide/carbon precursor composite secondary particles after cyclone collection.

Further, the carbonization equipment includes a tube furnace, an atmosphere box furnace, a pusher kiln, a roller kiln or a rotary furnace.

Specifically, the temperature of the carbonization reaction is 600-1200°C, and the time is 0.5-24 hours;

Specifically, the non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen, helium.

Specifically, the dispersing equipment includes any one of jet mill, ball mill, turbine mill, Raymond mill, coulter mill, and disc mill.

Specifically, the equipment for coating the additional carbon layer can be selected to have both heating and stirring functions, including but not limited to any one of a mechanical fusion machine, a VC mixer, a high-speed disperser, a coating tank or a reaction tank.

Further, the coating additional carbon layer may be selected from a chemical vapor deposition method, which includes the step of: performing chemical vapor deposition in organic gas and/or steam at a temperature of 700°C to 1050°C.

Compared with the prior art, the present invention has the following advantages:

In the present invention, the silicon oxide particles are closely connected through the carbon layer to form aggregated particles, and at the same time, the large-sized secondary particles are not increased too much, and the proportion of small-sized primary particles is reduced to obtain secondary particles with a narrower particle size distribution. Due to the preparation process of secondary particles, the scope of application of silicon oxide particle raw materials is improved, and the technical solution of the present invention also greatly reduces the specific surface area of the material, thereby reducing the use of the material in batteries such as lithium-ion secondary batteries. The contact area between the medium and the electrolyte reduces the loss of lithium ions caused by the continuous generation of SEI by the electrolyte on the surface of the material during each charge and discharge process, making the battery Coulombic efficiency higher and cycle performance better.

The carbon layer connection and coating also provide excellent electron and lithium ion transport channels, ensuring that the silicon oxide inside the particle fully participates in the electrochemical reaction, reduces the polarization of the battery, and improves the rate performance; when the secondary particles are dispersed inside and on the surface When there is a conductive additive, the conductivity of the material is further mentioned, and the rate performance of the battery is better.

Since the capacity and expansion rate of the silicon-oxygen composite material are higher than that of the carbon-based negative electrode blended with it, after the battery pole sheet is made, the micro-region where the silicon-oxygen composite material is usually located has a higher meeting capacity and larger expansion. Compared with silicon-oxygen composite materials prepared by other methods, the particle size distribution of the particles prepared by the present invention is narrow, and the proportion of large particles is less. The distribution is relatively more uniform, and the expansion rate of the pole piece will be smaller.

The present invention further coats the continuous carbon protective layer on the outer surface of the particles, further reduces the specific surface area of the composite material while increasing the electrical conductivity of the material, reduces the formation of SEI, and is beneficial to improving Coulombic efficiency and battery cycle retention rate. Since the structure of the material of the invention is more stable and the expansion is smaller, more silicon-oxygen particles can be added to the negative electrode material to achieve the purpose of increasing the energy density of the battery.

Description of drawings

FIG. 1 is a high-magnification scanning electron micrograph of secondary particles prepared in Example 1.

FIG. 2 is a schematic structural view of secondary particles prepared in Example 1.

3 is a schematic structural view of secondary particles prepared in Example 2.

4 is a schematic structural view of secondary particles prepared in Example 4.

Fig. 5 is a particle size distribution diagram of the silicon oxide raw material used in Comparative Example 2 and Example 6, and the secondary particles prepared in Comparative Examples 1, 2 and Example 6.

FIG. 6 is a low-magnification scanning electron micrograph of secondary particles prepared in Example 6.

FIG. 7 is a high-magnification scanning electron micrograph of secondary particles prepared in Example 6.

FIG. 8 is an electron micrograph of a cross-section of the negative electrode of the battery containing the secondary particles prepared in Example 6 after formation.

FIG. 9 is a high-magnification scanning electron micrograph of secondary particles prepared in Example 14.

FIG. 10 is a scanning electron micrograph of the particles prepared in Comparative Example 1.

FIG. 11 is a scanning electron micrograph of the particles prepared in Comparative Example 2.

detailed description

The specific embodiments of the present invention will be described in more detail below in conjunction with the examples, so as to better understand the solution of the present invention and its advantages in various aspects. However, the specific embodiments and examples described below are for the purpose of illustration only, rather than limiting the present invention.

Example 1

1. Preparation method

1.1 Preparation of secondary particles

Get 100kg of silicon oxide powder (that is: primary particle, D10=0.60 μm, D50=1.78 μm, D90=3.59 μm, SPAN=1.68, x=1 in SiOx general formula, specific surface area 8.9m ² /g) and 12kg coal Put the asphalt powder into the VC mixer, and mix for 30 minutes at a speed of 16m/s at the maximum diameter of the mixing part, so that the two raw materials are mixed evenly. Subsequently, the rotation speed was reduced to reduce the aforementioned linear velocity to 8m/s, and at the same time, nitrogen gas was introduced as an inert protective gas, and then the temperature was raised at a rate of 3°C/min, and the temperature was raised to 300°C and kept for 4h, and then naturally cooled to room temperature. Complete the granulation process of silicon oxide and pitch. During this process, as the temperature in the VC mixer rises, the asphalt gradually softens, and is evenly coated on the surface of each silicon oxide powder during continuous high-speed stirring. At the same time, the silicon oxide primary particles coated with asphalt Adhere to each other and agglomerate to form silica/asphalt composite secondary particles of a certain size. The above-mentioned secondary particles will become denser after a long time of shearing, extrusion, and collision in the VC mixer. At the same time, at a temperature of 300 ° C, the asphalt will partly remove small molecule volatiles, and partly cross-link and carbonize, so that The secondary particles are set.

Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a roller kiln, pass in a nitrogen protective gas to raise the temperature to 900°C at 3°C/min, keep it warm for 4h, and then cool naturally to room temperature to complete the carbonization treatment. In this step, the pitch is carbonized under high temperature treatment in an oxygen-free atmosphere. The above-mentioned carbonized products are subjected to airflow crushing treatment, and the soft aggregates of composite materials obtained after carbonization are broken up into fine secondary particle powders by adjusting the pressure of the crushing airflow without destroying the secondary particle structure. Finally, sieve and demagnetize to obtain the final product that can be used as negative electrode material.

Fig. 1 is a high-magnification scanning electron micrograph of the secondary particles prepared in Example 1, and Fig. 2 is a schematic structural diagram thereof. The particles prepared in Example 1 are dense secondary particles, which are connected by silicon oxide primary particles A and The coated carbon layer B is composited.

1.2 Preparation of pole piece

Take 9 parts of the above-mentioned secondary particles, 43.5 parts of artificial graphite, 43.5 parts of natural graphite, 1 part of conductive additive Super P, 0.5 part of multi-walled carbon nanotubes, 1 part of binder sodium carboxymethyl cellulose CMC, modified polyacrylic acid 1.5 parts of ester were homogenized in an aqueous system, coated, dried, and rolled to obtain a negative electrode sheet containing silicon-oxygen secondary particles.

2. Product testing

After testing, the particle size of the secondary particles is D10=1.89μm, D50=4.02μm, D90=7.16μm, SPAN=1.31, the specific surface area is 2.7m ² /g, the tap density is 0.88g/cm ³ , and the carbon content is 4.9 wt%. The disproportionation reaction will occur after the silicon oxide material is heat-treated above 800°C: 2SiO→Si+SiO ₂ , forming silicon nanocrystal grains/clusters uniformly dispersed in SiOx. According to the results of the X-ray diffraction pattern, substituting into the Sherrer equation, it can be calculated that the grain size corresponding to the Si(111) crystal plane in the material obtained in Example 1 is 2.9 nm.

The instruments and equipment used in the above testing items are:

The surface morphology of the samples was observed with a Hitachi SU8010 field emission scanning electron microscope.

Dandong Bettersize2000LD laser particle size analyzer was used to test the particle size and particle size distribution of the material.

The specific surface area of the material was tested by a Quantachrome Nova4200e specific surface area tester.

The tap density of the material was tested by Dandong Baite BT-301 tap density meter.

The carbon content in the material was determined by an elementar vario EL cube elemental analyzer.

The crystal structure of the material was tested using a Rigaku MiniFlex600 X-ray diffractometer.

3. Performance test

Half-battery evaluation: The above-mentioned silicon-oxygen-containing secondary particle negative electrode sheet, separator, lithium sheet, and stainless steel gasket were stacked in sequence, and 200 μL of electrolyte was added dropwise and then sealed to form a 2016-type lithium-ion half-battery. Use the small (micro) current range equipment of Wuhan Landian Electronics Co., Ltd. to test the capacity and discharge efficiency. The measured first-time reversible delithiation specific capacity of the half-cell of the negative electrode is 1593.3mAh/g, and the first-time charge-discharge coulombic efficiency is 78.6%.

Full battery evaluation: The silicon-oxygen-containing secondary particle negative electrode sheet prepared above was cut, vacuum baked, and paired with the positive electrode sheet (ternary nickel-cobalt-manganese material, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ) and separator After being wound and packed into an aluminum plastic case of a corresponding size, a certain amount of electrolyte is injected and sealed, and after formation, a complete lithium-ion full battery containing silicon-oxygen secondary particle negative electrodes can be obtained. Use the battery tester of Shenzhen Newwell Electronics Co., Ltd. to test the capacity of the full battery at 0.2C, the average voltage and the capacity retention data of 500 cycles at a charge and discharge rate of 1C. The tested voltage range is 4.2-2.75 V. After weighing the battery and combining the above electrochemical data, the gravimetric energy density of the full battery is calculated to be 301Wh/kg, the first Coulombic efficiency is 84.1%, and the capacity retention rate after 500 charge-discharge cycles is 85.3%. After 500 cycles, the battery is fully charged, and the thickness of the battery is measured. Compared with the initial thickness of the battery before cycling, the battery expansion rate is 9.0%. Then the battery is disassembled in an inert atmosphere, and the thickness of the negative electrode sheet filled with lithium is measured. , compared with the thickness of the negative pole piece before battery assembly, the full electric expansion rate of the negative pole piece is 29.4%. The above test results are summarized in Table 1.

Example 2

The process of Example 2 is similar to Example 1, the difference is that in the material synthesis process, in addition to taking 100kg of silicon oxide powder and 12kg of coal tar pitch powder into the VC mixer, an additional 0.3kg of Ketjen black and 0.2 kg of multi-walled carbon nanotube conductive additive powder. Therefore final product is the silicon oxide/amorphous carbon composite secondary particle that contains conductive additive, and its structure is as shown in Figure 3, and this material is made of silicon oxide primary particle A, conductive additive C and the two are connected and coated on The carbon layer B is compounded together, and the conductive additive C is uniformly dispersed in the interior and exterior surface of the secondary particle. D10=1.78 μm, D50=3.89 μm, D90=7.01 μm, SPAN=1.34 of the final product, specific surface area is 3.0m ² /g, tap density is 0.84g/cm ³ , carbon content is 5.3wt%, Si(111 ) crystal plane corresponds to a grain size of 2.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1. It can be seen that after adding the conductive additive, the battery performance has been improved to a certain extent.

Example 3

Get 100kg of secondary granules made in Example 1, and get 1kg of petroleum pitch powder, add VC mixer, mechanically mix under the condition of line speed 3m/s after 10 minutes, slow down to 2m/s, in nitrogen protection atmosphere The device was heated to 300° C. for 1 h while stirring, and then slowly cooled to room temperature. The above pitch-coated material was kept at 400°C for 2 hours in an argon inert atmosphere, then heated to 900°C for carbonization for 4 hours, naturally cooled to room temperature, crushed, sieved and demagnetized to obtain a second layer of amorphous Carbon coated silica/amorphous carbon composite particles. The final product has D10=2.13 μm, D50=4.65 μm, D90=7.87 μm, SPAN=1.23, specific surface area of 2.4m ² /g, tap density of 0.95g/cm ³ , carbon content of 5.8wt%, Si( 111) The grain size corresponding to the crystal plane is 2.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 4

Get the secondary granule 100kg that embodiment 2 makes, adopt the secondary coating process of embodiment 3 to process, obtain the silicon oxide/multi-walled carbon nanotube/ketjen black with the second layer of amorphous carbon coating layer / Amorphous carbon composite particles. Figure 4 is a schematic diagram of the structure of the secondary particles prepared in this example, as shown in Figure 4, the material is composed of silicon oxide primary particles A, conductive additive C and carbon layer B that connects and coats the two together , the conductive additive C is uniformly dispersed inside the secondary particles, and there is a second continuous carbon coating layer D on the outer surface of the secondary particles. The final product has D10=2.01 μm, D50=4.45 μm, D90=7.76 μm, SPAN=1.29, specific surface area of 2.7m ² /g, tap density of 0.89g/cm ³ , carbon content of 6.2wt%, Si( 111) The grain size corresponding to the crystal plane is 2.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1. It can be seen that, the same as in Example 3, after multiple coatings, the performance of the product can be significantly improved.

Example 5

Get 0.2kg sucrose and dissolve in 8kg deionized water to obtain sucrose solution, then add the carbon nanotube slurry containing 0.6g single-walled carbon nanotubes to the sucrose solution and stir to disperse, then add 2kg silicon oxide powder while stirring (same as implementing Example 1), followed by ultrasonic dispersion for 1 h while stirring to obtain a sucrose/single-walled carbon nanotube/silicon oxide particle composite slurry. The above-mentioned composite slurry was subjected to spray drying treatment, the air inlet temperature was 150° C., and the nozzle atomization pressure was 0.2 Mpa to obtain sucrose/single-walled carbon nanotubes/silicon oxide composite secondary particle dry powder. Put the above powder into a graphite sagger, put it in a box-type atmosphere furnace, pass nitrogen gas as an inert protective gas, raise the temperature to 900°C at 3°C/min, keep it warm for 6h, and cool naturally to room temperature to complete the carbonization treatment. The above-mentioned carbonized products are subjected to disc grinding treatment, and the maximum linear speed of the outer edge of the rotor of the disc grinding is 3m/s. Take 1kg of the above-mentioned secondary particles and 0.04kg of petroleum pitch powder, mix them briefly and add them into a mechanical fusion machine, control the linear speed of the outer edge of the rotor at 15m/s, fuse for 0.5h, and put the processed products in an inert atmosphere of nitrogen, Insulate at 400°C for 2h, then heat up to 900°C for carbonization for 4h, cool naturally to room temperature, crush, sieve and demagnetize to obtain silicon oxide/single-walled carbon nanotubes with a second layer of amorphous carbon coating / Amorphous carbon composite particles. The final product has D10=1.90 μm, D50=4.87 μm, D90=8.62 μm, SPAN=1.38, specific surface area of 3.7m ² /g, tap density of 0.82g/cm ³ , carbon content of about 4.8wt%, Si The grain size corresponding to the (111) crystal plane is 2.9 nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1. On the whole, although the battery performance of the spray-drying method has been improved compared with the prior art, compared with other examples , some of its indicators are not prominent.

Example 6

Take 100kg of silicon oxide powder (D10=1.07μm, D50=4.68μm, D90=8.84μm, SPAN=1.66, x=1 in SiOx general formula, specific surface area 2.9m ² /g) and 5kg of petroleum pitch powder into the vertical In the coating kettle, mix for 1 hour at a linear velocity of 7 m/s at the maximum diameter of the stirring part, so that the two raw materials are evenly mixed. Subsequently, the line speed was reduced to 3m/s, and nitrogen was introduced as an inert protective gas at the same time, and then the temperature was raised to 500°C at a rate of 3°C/min and kept for 3h, and then naturally cooled to room temperature. Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a roller kiln, pass in a nitrogen protective gas and raise the temperature to 1020°C at 3°C/min, keep it warm for 2h, and cool down to room temperature naturally. The above-mentioned carbonized products were subjected to coulter breaking treatment for 1 hour, and the coulter linear speed was 3m/s. Finally, sieving and demagnetization treatment are carried out, and the D10=4.32μm, D50=7.06μm, D90=10.90μm, SPAN=0.93 of the final product obtained, the specific surface area is 1.1m ² /g, and the tap density is 1.09g/cm ³ , the carbon content is 3.2wt%, and the grain size corresponding to the Si(111) crystal plane is 4.1nm.

FIG. 5 shows the particle size distribution diagram of the silicon oxide powder raw material and the silicon oxide composite material (ie, secondary particles) in this embodiment. In addition, Fig. 6 and Fig. 7 show the scanning electron micrographs of the secondary particles prepared in this example, and Fig. 8 is a cross-sectional electron micrograph of the lithium ion battery negative electrode sheet containing the secondary particles prepared in this example . It can be seen from Fig. 6 that the particles obtained in this example are secondary particles with uniform size and no monodisperse primary small particles. Referring to Fig. 7 and Fig. 8 at the same time, it can be seen that the particles prepared in this embodiment are dense secondary particles.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 7

Take 100kg of silicon oxide powder (same as in Example 6) and 9kg of polyvinyl alcohol powder into a vertical coating kettle, and mix for 2 hours at a speed of 5 m/s at the maximum diameter of the stirring part, so that the two raw materials are evenly mixed. Subsequently, the line speed was reduced to 3m/s, and nitrogen was introduced as an inert protective gas at the same time, and then the temperature was raised to 300°C at a rate of 2°C/min and kept for 6h, followed by natural cooling to room temperature. Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a roller kiln, pass in a nitrogen protective gas and raise the temperature to 1020°C at 3°C/min, keep it warm for 2h, and cool down to room temperature naturally. The above-mentioned carbonized products were subjected to coulter breaking treatment for 1 hour, and the coulter linear speed was 3m/s. Finally, sieving and demagnetization treatment are carried out, and the D10=3.97μm, D50=6.91μm, D90=10.40μm, SPAN=0.93 of the final product obtained, the specific surface area is 1.2m ² /g, and the tap density is 1.05g/cm ³ , the carbon content is 3.0wt%, and the grain size corresponding to the Si(111) crystal plane is 4.1nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 8

Take 100kg of silicon oxide powder (D10=0.87μm, D50=3.88μm, D90=7.73μm, SPAN=1.77, x=1 in SiOx general formula, specific surface area 3.8m ² /g) and 7kg of petroleum asphalt powder and add VC to mix In the machine, mix for 1 hour at a speed of 8m/s at the maximum diameter of the stirring part, so that the two raw materials are mixed evenly. Subsequently, the line speed was reduced to 4 m/s, and nitrogen was introduced as an inert protective gas at the same time, and then the temperature was raised to 900 °C at a rate of 3 °C/min and kept for 1 h, and then naturally cooled to room temperature. Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a pusher kiln, pass in a nitrogen protective gas and raise the temperature to 1000°C at 3°C/min, keep it warm for 3h, and cool down to room temperature naturally. The above-mentioned carbonized products were subjected to coulter breaking treatment for 1 hour, and the coulter linear speed was 3m/s. Finally, sieving and demagnetization treatment are carried out, and the D10=4.51μm, D50=7.15μm, D90=11.07μm, SPAN=0.92 of the final product obtained, the specific surface area is 1.0m ² /g, and the tap density is 1.12g/cm ³ , the carbon content is 4.0wt%, and the grain size corresponding to the Si(111) crystal plane is 3.9nm.

The evaluation method of the half-cell and the full-cell is the same as in Example 1, and the results are summarized in Table 1. The gravimetric energy density of the full-cell reaches 311Wh/kg, the cycle retention rate reaches 90.7%, and the battery expansion rate is 7.6%. The obtained battery has excellent performance.

Example 9

The process steps of Example 9 are similar to those of Example 8, the only difference is that in the granulation step, the holding temperature in the VC mixer is 400° C., and the holding time is 3 hours. D10=4.26μm, D50=7.46μm, D90=11.98μm, SPAN=1.03 of the final product, specific surface area is 1.2m ² /g, tap density is 1.07g/cm ³ , carbon content is 3.9wt%, Si(111 ) crystal plane corresponds to a grain size of 3.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 10

The process steps of Example 10 are similar to those of Example 8, the only difference is that in the granulation step, the holding temperature in the VC mixer is 150° C., and the holding time is 6 hours. D10=4.00 μm, D50=8.47 μm, D90=14.10 μm, SPAN=1.19 of the final product, the specific surface area is 1.4m ² /g, the tap density is 1.02g/cm ³ , the carbon content is 3.9wt%, Si(111 ) crystal plane corresponds to a grain size of 3.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 11

The process step of embodiment 11 is similar to embodiment 9, only difference is that the petroleum pitch amount that adds is 9kg. D10=4.78μm, D50=8.90μm, D90=14.90μm, SPAN=1.14 of the final product, the specific surface area is 1.6m ² /g, the tap density is 1.01g/cm ³ , the carbon content is 6.1wt%, Si(111 ) crystal plane corresponds to a grain size of 3.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 12

The processing step of embodiment 12 is similar to embodiment 9, only difference is that the petroleum pitch amount that adds is 3kg. D10=3.78μm, D50=6.98μm, D90=10.76μm, SPAN=1.00 of the final product, the specific surface area is 1.1m ² /g, the tap density is 1.11g/cm ³ , the carbon content is 2.7wt%, Si(111 ) crystal plane corresponds to a grain size of 3.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 13

Take 2kg silicon oxide powder (D10=3.62μm, D50=7.90μm, D90=13.40μm, SPAN=1.24, x=1 in SiOx general formula, specific surface area 1.8m ² /g) and 0.08kg coal tar pitch powder, 0.01 Add kg of vapor-phase-grown carbon fiber powder into the mechanical fusion machine, and mix for 10 minutes at a speed of 20 m/s at the outer edge of the rotor, so that the three raw materials are evenly mixed. Then keep the line speed of 20m/s, heat up to 180°C and keep it for 0.5h, then cool down to room temperature naturally. Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a tube furnace, pass in nitrogen protective gas and raise the temperature to 930°C at 3°C/min, keep it warm for 8h, and cool down to room temperature naturally. The above-mentioned carbonized products are subjected to disc grinding treatment, and the maximum linear speed of the outer edge of the rotor of the disc grinding is 3m/s. Finally, sieving and demagnetization treatment are carried out, and the D10=5.91μm, D50=10.21μm, D90=17.60μm, SPAN=1.14 of the final product obtained, the specific surface area is 1.1m ² /g, and the tap density is 1.10g/cm ³ , the carbon content is 3.2wt%, and the grain size corresponding to the Si(111) crystal plane is 3.1nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 14

Take 100kg of silicon oxide powder (D10=2.44μm, D50=4.55μm, D90=6.99μm, SPAN=1.00, x=1 in SiOx general formula, specific surface area 1.7m ² /g) and 6kg of coal tar pitch powder into the vertical In the coating tank, mix for 1 hour at a linear velocity of 6 m/s at the maximum diameter of the stirring part, so that the two raw materials are evenly mixed. Subsequently, the line speed was reduced to 2 m/s, and nitrogen was introduced as an inert protective gas at the same time, and then the temperature was raised to 300 °C at a rate of 3 °C/min and kept for 6 h, and then naturally cooled to room temperature. Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a pusher kiln, pass in a nitrogen protective gas and raise the temperature to 950°C at 3°C/min, keep it warm for 5h, and cool down to room temperature naturally. The above-mentioned carbonized products are subjected to disc grinding treatment, and the maximum linear speed of the outer edge of the rotor of the disc grinding is 3m/s. Finally, sieving and demagnetization treatment are carried out, and the D10=4.92μm, D50=8.32μm, D90=14.70μm, SPAN=1.18 of the final product obtained, the specific surface area is 1.2m ² /g, and the tap density is 1.07g/cm ³ , the carbon content is 3.2wt%, and the grain size corresponding to the Si(111) crystal plane is 3.7nm. FIG. 9 is a high-magnification scanning electron micrograph of secondary particles prepared in Example 14.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Example 15

Get 100kg silicon oxide powder (same as Example 14) and 6kg coal tar pitch powder, 0.5kg Super P and add in the vertical cladding kettle, mix 1h under the speed of linear velocity 6m/s at the maximum diameter place of stirring member, make three kinds The ingredients are mixed well. Subsequently, the line speed was reduced to 2 m/s, and nitrogen was introduced as an inert protective gas at the same time, and then the temperature was raised to 300 °C at a rate of 3 °C/min and kept for 6 h, and then naturally cooled to room temperature. Take the above-mentioned intermediate product and put it into a graphite sagger, put it in a pusher kiln, pass in a nitrogen protective gas and raise the temperature to 950°C at 3°C/min, keep it warm for 5h, and cool down to room temperature naturally. The above-mentioned carbonized products are subjected to disc grinding treatment, and the maximum linear speed of the outer edge of the rotor of the disc grinding is 3m/s. Take 2kg of the dispersed material and place it in a rotary furnace, raise the temperature to 950°C at 3°C/min, feed acetylene and nitrogen at flow rates of 0.2L/min and 0.3L/min respectively, react for 5 hours, cool to room temperature and take it out. Finally, sieving and demagnetization treatment are carried out, and the D10=5.38μm, D50=8.80μm, D90=15.60μm, SPAN=1.16 of the final product obtained, the specific surface area is 1.8m ² /g, and the tap density is 0.99g/cm ³ , the carbon content is 5.2wt%, and the grain size corresponding to the Si(111) crystal plane is 3.7nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Comparative example 1

Place the silicon oxide block (average particle size is about 2cm) in a box-type furnace, pass through the argon protective atmosphere, heat it at 3°C/min to 1000°C for 2 hours, and obtain a disproportionated modified silicon oxide block body. The disproportionated silicon oxide block was crushed and pulverized, and the obtained material had D10=1.04 μm, D50=4.61 μm, D90=9.01 μm, and SPAN=1.73. Take 2000g of silicon oxide powder and place it in a rotary furnace, raise the temperature to 900°C at a rate of 3°C/min, feed acetylene gas at a flow rate of 0.2L/min, and feed a nitrogen protective atmosphere into the furnace during the entire reaction process, and control the flow rate to 0.1L/min, react for 10h to obtain the precursor; put the above precursor into the mechanical fusion machine, control the linear speed at the outer edge of the rotor to 15m/s, fuse for 10min, then mix, sieve, demagnetize, dry and Packaged to obtain a silicon oxide composite material with D10=2.05μm, D50=5.25μm, D90=9.54μm, SPAN=1.43, a specific surface area of 5.2m ² /g, a tap density of 0.93g/cm ³ , and a carbon content of about 5.2wt%, the grain size corresponding to the Si(111) crystal plane is 4.0nm.

Figure 10 is an electron microscope picture of the silicon oxide composite material in Comparative Example 1. It can be seen that there are many fine powder particles in the composite material, mostly monodisperse primary particles, and the particles have sharp edges and corners. It can be seen from the particle size distribution diagram of the silicon oxide composite material in Comparative Example 1 in Fig. 5 that the particle size distribution of the product of Comparative Example 1 is wider than that of Example 6, and the proportion of small particles is higher. The particle size distribution curve in Figure 5 is a weight/volume distribution curve, and the curve height of the small particle section is higher, indicating that the weight/volume ratio of small particles is higher, and the number ratio and specific surface area ratio converted into small particles are orders of magnitude Increase. Therefore, it can be seen from the figure that compared with Example 6, the proportion of small particles in Comparative Example 1 is much higher, and the specific surface area also increases greatly.

Referring to the half-cell and full-cell evaluation methods in Example 1, the performance of the battery prepared by the particles of the comparative example was evaluated, and the results are summarized in Table 1.

Comparative example 2

Put 100 kg of silicon oxide powder (same as Example 6) and 10 kg of petroleum pitch powder in a VC mixer, adjust the line speed to 10 m/s, and mix for 0.5 h to obtain precursor 1. Add the precursor 1 into the vacuum kneader, control the temperature of the material above 250°C by heating and circulating heat-conducting oil, knead for 6 hours until the material becomes viscous, and then quickly transfer the material to the flaking machine for flaking treatment before the material cools down. The thickness of the rolled flakes is 2.0-5.0mm. After the rolled flakes are cooled, mechanical crushing is carried out, and the median particle size is controlled to be 2.0-15.0 μm. Then, the crushed materials are subjected to constant temperature and isostatic pressing. The controlled pressure is 20MPa and the temperature is 250°C. , implementing 0.1h pressure treatment to obtain precursor 2. Precursor 2 was placed in a roller kiln, and the temperature was raised to 1000°C at 3°C/min by introducing nitrogen protective gas, kept for 7 hours, and cooled naturally to room temperature. Then carry out coulter crushing for 1 hour, and the maximum linear speed of the coulter is 3 m/s, and then carry out sieving, demagnetization, and drying to obtain silicon oxide particles. D10 = 3.22 μm, D50 = 6.77 μm, D90 = 13.36 μm, SPAN = 1.50, specific surface area 2.2m ² /g, tap density 0.99g/cm ³ , carbon content about 6.3wt%, Si( 111) The grain size corresponding to the crystal plane is 4.0nm.

Figure 11 is an electron microscope picture of silicon oxide particles in Comparative Example 2. It can be seen that there are more fine powder particles in the composite material, and there are more monodisperse primary particles, and there are loose particles with large specific surface area composed of some large and small primary particles. secondary particles. It can be seen from the particle size distribution diagram of silicon oxide particles in Comparative Example 2 in Figure 5 that the particle size distribution of the product of Comparative Example 2 is wider than that of Example 1, and the proportion of small particles and large particles is relatively high.

Referring to the half-cell and full-cell evaluation methods in Example 1, the performance of the battery prepared by the particles of the comparative example was evaluated, and the results are summarized in Table 1.

Comparative example 3

The process steps of Comparative Example 3 are similar to those of Examples 8-10, the only difference is that after the VC mixer is used for mixing at room temperature, the granulation process is not carried out with heating and stirring, and the material is directly discharged, and the material is subjected to subsequent carbonization and crushing , Sieving, demagnetization treatment. D10=1.93 μm, D50=8.68 μm, D90=16.22 μm, SPAN=1.65 of the final product, the specific surface area is 2.2m ² /g, the tap density is 1.02g/cm ³ , the carbon content is 3.9wt%, Si(111 ) crystal plane corresponds to a grain size of 3.9nm.

The half-cell and full-cell evaluation methods are the same as in Example 1, and the results are summarized in Table 1.

Table 1 Summary of performance test data

For the prior art, its preparation process is complex, such as processes such as kneading, rolling, and compression molding, which are difficult to achieve large-scale production. Moreover, after the carbonization of the carbon precursor, it is bound to stick and agglomerate the adjacent silicon oxide particles, and the subsequent crushing and crushing processes will cause damage to the carbon coating. The particle size distribution of the material prepared by the existing technology is relatively wide, and the proportion of large and small particles is relatively high. The coulombic efficiency, expansion rate, and cycle retention rate of the battery produced are not ideal, and the areal capacity and micro-domain expansion distribution are not uniform. However, the secondary particles used in negative electrode materials prepared by the present invention are dense, have narrow particle size distribution, and small specific surface area. After testing, they have the advantages of high capacity, high Coulombic efficiency, uniform surface capacity distribution, low expansion, and high cycle retention rate. . The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any skilled person who is familiar with the profession, without departing from the scope of the technical solutions of the present invention, according to the technical essence of the present invention, Any simple modifications, equivalent replacements and improvements made in the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims (18)

1. A silica particle comprising a silica particle and a carbon layer;

wherein the mass proportion of the silica particles in the silica particles is 90-99.5wt%; the plurality of silicon oxide particles are bonded by the carbon layer, and the plurality of silicon oxide particles bonded by the carbon layer are coated by the carbon layer.

2. The silicone particle according to claim 1, wherein the carbon layer is obtained by carbonizing a combination of one or more precursor materials selected from glucose, sucrose, chitosan, starch, citric acid, gelatin, alginic acid, carboxymethyl cellulose, coal pitch, petroleum pitch, phenol resin, tar, naphthalene oil, anthracene oil, polyacrylic acid, polyacrylate, polystyrene, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, epoxy resin, polyacrylonitrile, and polymethyl methacrylate.

3. The silicon dioxide particles according to claim 1, characterised in that the median particle diameter D50 of the silicon dioxide particles is 0.05 to 20 μm, preferably 0.3 to 10 μm.

4. Silicon dioxide particles according to claim 1, characterised in that the D50 of the silicon dioxide particles is from 1 to 40 μm, preferably from 3 to 20 μm, more preferably from 3.5 to 10 μm.

5. The silicone particle according to claim 4, wherein the particle size of the silicone particle satisfies: (D90-D10)/D50. Ltoreq.1.4, preferably. Ltoreq.1.35.

6. The silicone particles according to claim 1, wherein the specific surface area of the silicone particles is from 0.1 to 10m ² A/g, preferably of 0.3 to 6m ² A ratio of 0.8 to 2.7 m/g is more preferable ² /g。

7. The silica particles according to claim 1, wherein the silica particles have a tap density of not less than 0.6g/cm ³ Preferably not less than 0.8g/cm ³ 。

8. A silica particle comprising a silica particle, a first carbon layer, and a conductive additive;

wherein the mass proportion of the silica particles in the silica particles is 90-99.5wt%; a plurality of the silicon oxide particles are bonded by the first carbon layer, and the silicon oxide particles bonded by the first carbon layer are coated by the first carbon layer; the conductive additive is uniformly dispersed in the silicon oxide particles and on the outer surface of the silicon oxide particles;

wherein the conductive additive is selected from one or more of Super P, ketjen black, vapor grown carbon fiber, acetylene black and carbon nanotube.

9. The silicone particle of claim 8, wherein said conductive additive comprises from 0.01 to 5wt% of said silicone particle.

10. The silicon oxide particle according to claim 8, further comprising a second carbon layer coated on the outer surface of the silicon oxide particle.

11. The silica particle according to claim 10, wherein the second carbon layer is obtained by carbonizing a combination of one or more precursor materials selected from coal pitch, petroleum pitch, polyvinyl alcohol, epoxy resin, polyacrylonitrile, and polymethyl methacrylate, or by chemical vapor deposition of any one or more precursor materials selected from methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, butadiene, benzene, toluene, xylene, styrene, and phenol.

12. The silicone particle according to claim 10, wherein the second carbon layer accounts for 0.1 to 6wt% of the silicone particle.

13. Use of the silicon oxygen particles as claimed in any of claims 1 to 12 in electrode materials.

14. A negative electrode material comprising the silica particles according to any one of claims 1 to 12.

15. A pole piece or battery comprising the negative electrode material of claim 14.

16. The method of making a silicone particle of claim 1, comprising:

mixing and granulating a raw material of the silicon monoxide powder and a precursor material of the carbon layer, carbonizing in a non-oxidizing atmosphere, and scattering, sieving and demagnetizing a carbonized product.

17. The method of preparing a silicone particle according to claim 8, comprising:

mixing and granulating a raw material of the silicon monoxide powder, a precursor material of the carbon layer and a conductive additive, carbonizing in a non-oxidizing atmosphere, and scattering, sieving and demagnetizing a carbonized product.

18. The method of producing silicone particles according to claim 17,

further comprising coating a second carbon layer.

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